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December 10, 2012

Do we live in a computer simulation? UW researchers say idea can be tested

Is this supported by the fact the Voyager 1 found an unexpected band of magnetic energy at the edge of the solar system? Voyager 1 finds a surprise at the edge of the solar system..NASA's Voyager 1, which is headed for interstellar space, runs into an unexpected 'magnetic highway.'

Do we live in a computer simulation? UW researchers say idea can be tested

A decade ago, a British philosopher put forth the notion that the universe we live in might in fact be a computer simulation run by our descendants. While that seems far-fetched, perhaps evenincomprehensible, a team of physicists at the University of Washington has come up with a potential test to see if the idea holds water.

The concept that current humanity could possibly be living in a computer simulation comes from a 2003 paper published in Philosophical Quarterly by Nick Bostrom, a philosophy professor atthe University of Oxford. In the paper, heargued that at least one of three possibilities is true:

The human species is likely to goextinct before reaching a “posthuman” stage.

Any posthuman civilization is veryunlikely to run a significant number of simulations of its evolutionaryhistory.

We are almost certainly living in acomputer simulation.

He also held that “the belief that there is a significant chance that wewill one day become posthumans who run ancestor simulations is false, unless weare currently living in a simulation.”

The conical (red) surface shows the relationship between energy and momentum in special relativity, a fundamental theory concerning space and time developed by Albert Einstein, and is theexpected result if our universe is not a simulation. The flat (blue) surfaceillustrates the relationship between energy and momentum that would be expectedif the universe is a simulation with an underlying cubic lattice

With current limitations and trends in computing, it will be decadesbefore researchers will be able to run even primitive simulations of theuniverse. But the UW team has suggested tests that can be performed now, or inthe near future, that are sensitive to constraints imposed on futuresimulations by limited resources.

Currently, supercomputers using a technique called lattice quantumchromodynamics and starting from the fundamental physical laws that govern theuniverse can simulate only a very small portion of the universe, on the scaleof one 100-trillionth of a meter, a little larger than the nucleus of an atom,said Martin Savage,a UW physics professor.

Eventually, more powerful simulations will be able to model on the scaleof a molecule, then a cell and even a human being. But it will take manygenerations of growth in computing power to be able to simulate a large enoughchunk of the universe to understand the constraints on physical processes thatwould indicate we are living in a computer model.

However, Savage said, there are signatures of resource constraints inpresent-day simulations that are likely to exist as well in simulations in thedistant future, including the imprint of an underlying lattice if one is usedto model the space-time continuum.

The supercomputers performing lattice quantum chromodynamicscalculations essentially divide space-time into a four-dimensional grid. Thatallows researchers to examine what is called the strong force, one of the fourfundamental forces of nature and the one that binds subatomic particles calledquarks and gluons together into neutrons and protons at the core of atoms.

“If you make the simulations big enough, something like our universeshould emerge,” Savage said. Then it would be a matter of looking for a“signature” in our universe that has an analog in the current small-scalesimulations.

Savage and colleagues SilasBeane of the University of New Hampshire, whocollaborated while at the UW’s Institutefor Nuclear Theory, and Zohreh Davoudi, a UW physics graduate student,suggest that the signature could show up as a limitation in the energy ofcosmic rays.

In a paper they have posted on arXiv, an online archive for preprints of scientific papers in a number of fields, including physics, they say that the highest-energy cosmic rays wouldnot travel along the edges of the lattice in the model but would traveldiagonally, and they would not interact equally in all directions as theyotherwise would be expected to do.

“This is the first testable signature of such an idea,” Savage said.

If such a concept turned out to be reality, it would raise otherpossibilities as well. For example, Davoudi suggests that if our universe is asimulation, then those running it could be running other simulations as well,essentially creating other universes parallel to our own.

“Then the question is, ‘Can you communicate with those other universesif they are running on the same platform?’” she said.